FINDINGS IN GLASS TECHNOLOGY REPORTED FROM R.M. HOVHANNISYAN AND CO-RESEARCHERS

Technology Business Journal
November 10, 2009

"The phase diagram of the binary Y2O3-B2O3 system has been revised,
the phase diagram in the pseudo-binary YAlO3-YBO3 system has been
constructed and two binary eutectics have been revealed. A new tertiary
eutectic between YAlO3, YBO3 and an unknown ternary yttrium aluminium
compound has been revealed," investigators in Yerevan, Armenia report.

"Glass forming ability in the tertiary Y2O3-Al2O3-B2O3 system has
been investigated and a glass forming diagram dependant on melt
casting procedure has been determined. The expanded glass formation
area occupies fields of composition with low liquidus, formed between
binary yttrium aluminate, yttrium borate and yttrium aluminium borate
eutectics. The crystalline phase formation in yttrium aluminium
tetraborate have been determined by solid state sintering and by
devitrification of the corresponding glass composition in powder,
bulk and tape form. The binary aluminium and yttrium borates are
formed as the first step (750-850 degrees C) of solid state sintering
and all forms of glass devitrification. Differential thermal analysis
and x-ray diffraction showed the dominant tertiary yttrium aluminium
tetraborate phase formation at 1000-1135 degrees C in solid sintering
batches and glass powder crystallisation. This phase is formed in
the range 800-950 degrees C for bulk glass and tape crystallisation,"
wrote R.M. Hovhannisyan and colleagues.

The researchers concluded: "The glass ceramics based on yttrium
aluminium tetraborate are ferroelectric, with remanent polarization
equal to 0.08-0.3 mu C/cm(2) at external field 200-240 kV/cm."

Hovhannisyan and colleagues published their study in Glass Technology
– European Journal of Glass Science and Technology Part a (Glass
formation and crystallisation behaviour of yttrium aluminium
tetraborate glass-ceramic. Glass Technology – European Journal of
Glass Science and Technology Part a, 2009;50(4):221-226).

For additional information, contact R.M. Hovhannisyan, Science Prod
Enterprise Materials Science, 17 Charents St., Yerevan 0025, Armenia.

The publisher of the Glass Technology – European Journal of Glass
Science and Technology Part a can be contacted at: Society Glass
Technology, Unit 9, Twelve O Clock Court, 21 Attercliffe Rd., Sheffield
S4 7WW, S Yorkshire, England.